This application claims priority to German application No 198 48 002.4, filed Oct. 17, 1998, herein incorporated by reference.
1. Field of the Invention
The present invention relates to polypeptide-polysiloxane copolymers, to their preparation by thermal copolymerization of amino acids with organofunctional polysiloxanes, and to their use as interface-active substances.
2. Description of the Art
Proteins are naturally occurring polypeptides and play an important role in all biological processes. They are being used increasingly in personal care products as conditioners, humectants and emollients. Proteins are natural, high molecular weight polymers and are generally hydrolyzed to low molecular weight proteins so that they are soluble in water. Although protein hydrolyzates can be incorporated more easily into formulations, the soluble proteins are less substantive on skin and hair.
Silicone is the collective term for a large number of compounds with varying properties, but which are all characterized by the silicon-oxygen bond in the siloxane chain. Like proteins, they likewise play an important role in personal care, in particular as conditioners. Polydimethylsiloxanes, for example, are substantive on skin and hair, make hair shiny and smooth and produce a pleasantly soft and silky feel on the skin. However, they are virtually insoluble in water. Although silicone polyethers are water-soluble silicone derivatives which are able to make the hair smooth, they are not very substantive.
Proteins and silicones are thus two very different classes of substances having likewise different properties and advantages which are useful in each case for cosmetic applications. The development of proteins, which also have some of the characteristic properties of silicones such as the smoothing of hair and skin, or of silicones, which have the advantages of proteins such as better solubility in water and higher substantivity, has given access to products with properties which cannot be obtained by simple mixtures of the two classes of substances.
U.S. Pat. No. 3,562,353 has already described the combination of silicones with polypeptides in the form of copolymers. These are block copolymers of the ABA or (AB)n type, which are obtained by coupling end-functionalized homopolymers. A is a polyamide moiety having a molecular mass of from 2,000 to 100,000 and B is a silicone moiety having a molecular mass of from 500 to 100,000. The compounds are thermoplastic block copolymers which are either elastic or solid and can be used as biocompatible implant materials. They are prepared by the reaction of a polyamide consisting of alpha-amino acids and having reactive end groups such as hydroxyalkyl, aminoalkyl or isocyanato groups with a silicone which carries reactive end groups such as chloroalkyl, carboxyl, isocyanato, hydroxyalkyl or aminoalkyl groups. However, the functional polyamide must first be prepared with additional synthetic expenditure including protection-group chemistry. In a first stage, the corresponding N-carboxyanhydride is prepared from the alpha-amino acid by reaction with phosgene in a solvent such as dioxane. If the alpha-amino acid is a dicarboxylic acid such as glutamic acid or aspartic acid, then one carboxyl group must first be esterified by esterification, for example, with an excess of benzyl alcohol in the presence of hydrobromic acid. If it is an alpha-amino acid containing another amino, hydroxyl or mercapto group, these must then likewise be protected in a suitable manner prior to the reaction with phosgene in order to avoid undesired side reactions. In a second stage, the protected alpha-amino acid is then reacted to give the polyamide. This multistage synthesis may be illustrated more detailed by means of the following example Starting from the N-carboxyanhydride, protected in the form of the benzyl, ester, of L-glutamic acid, N-carboxy-gamma-benzyl L-glutamate is prepared. Then this is polymerized with ethanolamine as initiator in dimethylformamide as solvent. After about 90% conversion, the N-carboxyanhydride of phenylalanine must be added so that it forms the end group of the polyamide. The polymer formed must be precipitated in water and washed with methanol. In the next step, the polyamide is heated in epsilon-caprolactone as reagent and solvent for over 50 h (!), then precipitated again in water and washed with methanol. This gives a polyamide which carries hydroxyalkyl groups at both ends. The dihydroxy-functional polyamide is then reacted in a mixture of benzene and dichlorobenzene as solvent with alpha, omega-bis(dimethylamino)poly(dimethylsiloxane) with the elimination of dimethylamine. The polymer is precipitated out with methanol and washed with hexane. Thus, to prepare the copolymers described in U.S. Pat. No. 3,562,353, a large number of reaction and work-up steps are required, including complex protection-group chemistry. In addition, some of the reagents required are very toxic, such as phosgene, and the reactions are carried out in solvents such as benzene and dimethylformamide, from which the product must be recovered. As a rule, the polypeptide moiety contains amino acids containing protective groups, such as benzylglutamic acid and nonpolar amino acids such as phenylalanine. The copolymers are thus virtually insoluble in water. On the other hand, the linking between polyamide and silicone moiety is carried out via a hydrolysis-sensitive Sixe2x80x94Oxe2x80x94C bond, meaning that if the protective groups were removed, the bond between silicone and peptide moieties would be cleaved again and additionally degradation reactions on the polysiloxane would be triggered
Journal of Applied Polymer Science, 27, 1982, 139-148 likewise describes the preparation of polypeptide-polysiloxane block copolymers. These are obtained by polymerization of the N-carboxyanhydrides of phenylalanine and gamma-benzylglutamic acid with an alpha, omega-aminopropyl-functional polydimethylsiloxane as initiator. The resulting block copolymers are white, soft solids. However, as in U.S. Pat. No. 3,562,353, the preparation of the copolymers requires a large number of reaction and work-up steps, as well as protective groups and solvents. A typical reaction time for the polymerization is in the range between 100 and 200 h (!).
U.S. Pat. No. 5,100,956 claims silicone-protein copolymers in which the silicone moiety is linked to the amino group of a protein via a polyether phosphate group. Although the polyether phosphate unit makes the polymers soluble in water, they also have a very hydrolysis-sensitive phosphoric ester function, meaning that the silicone and protein moieties can again be readily cleaved from one another. In addition, it must be accepted that the polyether residues, which act as spacers and linking element between protein and silicone moieties, because of their polymer distribution and the high molecular weight character associated therewith, do not leave the properties of the product unaffected and have the property profile of hybrid silicone-polyether protein copolymers rather than act as pure silicone-protein copolymers. The silicone-protein copolymers are prepared by reacting water-soluble epoxy-functional polysil(ox)anes with hydrolyzates of natural proteins in water. The solubility of the polysiloxanes in water is here achieved by hydrosilylating addition reaction of polyethers and subsequent phosphatation of the hydroxyl group. An epoxy group, which is able to react with free amino groups of the protein, is then introduced into the silicone by reaction of the sodium salt of the silicone phosphate with epichlorohydrin. Thus synthesis route also has several stages and uses hazardous and highly toxic reagents such as phosphorus pentoxide or epichlorohydrin.
Another U.S. Patent U.S. Pat. No. 5,243,028, also describes an improved process variant for the preparation of silicone-protein copolymers. This involves firstly reacting a hydroxy-functional silicone polyether with chloroacetic acid to give the corresponding chloroacetate-functional siloxane. This is then followed by the reaction with proteins or protein hydrolyzates under defined conditions, where, within the scope of a substitution reaction, the organically bonded chlorine is converted into the chloride form and linking to the protein takes place. Although this process is an overall improvement, it is not possible to refrain from the use of caustic and toxic chloroacetic acid here either. It is a further disadvantage that the linking between silicone residues and the protein radical takes place via an ester group which is not stable to hydrolysis. This severely limits the use of such materials in aqueous formulations and even makes long-term storage under aqueous conditions impossible. Furthermore, it has to be feared that such products, because of the hygroscopic properties of the protein radical, are themselves not insufficiently stable in solid form and that, as the storage time increases, an increase of a retro-cleavage to the silicone polyether and free protein will take place. If, as described in the examples, silicone polyethers are used as starting materials, the products are not true silicone proteins here either, but have significant hybrid character.
EP-A-0 540 357 (Croda, GB 9 123 251, November 1991) claims protein-silicone copolymers in which the silicone component is covalently bonded to the amino groups of the protein. In each case at least some of the silicone components contribute to the crosslinking between various protein chains, but additionally noncrosslinking siloxane units may also be present. Serving as protein component are natural proteins such as collagen, elastin etc., which have either been partially hydrolyzed or have been modified by chemical modification such as esterification or quatemization. The copolymers are formed by reaction of functional groups of silanes or silicones with the amino groups of the protein. This produces higher molecular weight polymers which also contain protein chains crosslinked with one another. Additional crosslinking can take place as a result of the condensation of silanol groups of the silanes or silicones. An important requirement for the reaction of the protein component is its solubility in water or another suitable solvent such as ethanol or propylene glycol or in mixtures thereof. Another prerequisite is the ability of the silicone component to effect crosslinking with the protein component. Required for this purpose are either polyfunctional silicones with suitable reactive groups such as acid halide, anhydride or epoxide groups, or monofunctional silicon compounds which contain silanol groups or groups which can form silanol groups by hydrolysis in situ, which cause crosslinking as a result of condensation to siloxane bonds. In order for the silicon compound to react with the protein, it must be soluble in the same solvent as the protein, which is preferably an aqueous protein hydrolyzate. Therefore, if water is solvent, an organofunctional silane with hydrolyzable groups is required. Here, the reaction conditions must be controlled very carefully. This is because first a pH above 7 is usually required so that the amino groups of the protein are reactive, and, second, rapid hydrolysis of the cleavable groups usually takes place under alkaline conditions. However, at the same time, a condensation of the silane takes place, meaning that the overall reaction can be controlled only with difficulty. This method, therefore, gives only crosslinked products. Since such products do not contain linear polydimethylsiloxane segments, their typical silicone properties are not very pronounced either. In addition, the products can be handled only in the form of aqueous solutions since a solid, water-insoluble film forms as soon as the water is removed by distillation or drying. The reaction can, for example, be carried out in ethanol so that organofunctional dimethylsilicones, which are insoluble in water, but soluble in ethanol at least in small amounts, can be used. However, it is necessary to use the ethyl ester of the protein hydrolyzate, which again involves additional reaction steps. In addition, the pH required for the reaction is adjusted using sodium hydroxide, which, at reaction temperatures around 70xc2x0 C., can cause undesired siloxane chain degradation. It is stated that the chemical structure of the protein-silicone copolymers is very complex and it is therefore impossible to assign to them an individual general structural formula.
EP-A-0 699 431 claims silylated peptides in which the amino group of a peptide carries only one silyl group. The linking between silicon compound and peptide is produced in a similar manner to EP-A-0 540 357 by reaction of the amino groups of the peptide with a reactive group of the silicon compound. The silicon compound used is a silane with a haloalkyl group. In order that the hydrophilic peptides can react with the hydrophobic silyl compounds in water, the other groups of the silane must first be hydrolyzed so that the silane becomes soluble in water. When haloalkylsilanes are used, a hydrohalic acid forms, which lowers the pH of the reaction mixture. For this reason, the pH of the reaction mixture must be kept constant by addition of sodium hydroxide so that the reaction of the halogen group with water is avoided. In order that at least two silyl groups can be introduced per peptide, the peptide must contain amino acids with an additional amino group, as is the case with lysine. The silicon content is thus only inserted in the form of silyl groups and, more specifically, of only one silyl group per amino group of the protein. For this reason, as in EP-A-0 540 357, a dimethylsilicon effect is not to be expected in the case of the silane-based protein-silicone copolymers either.
Natural proteins and synthetic peptides are linear polymers of amino acids which are linked together via an amide bond (peptide bond). However, when an amino acid is heated to above 100xc2x0 C., a polymer is not usually obtained. Rather, a rapid black discoloration is observed, which can be attributed inter alia to the formation of heterocycles. Exceptions to this are aspartic acid, which forms polysuccinimide upon heating, which can be converted into polyaspartic acid under basic conditions. Glutamic acid cyclizes upon heating to give monomeric pyroglutamic acid (2-pyrrolidone-5-carboxylic acid). In the early 1950s, Fox and Middlebrook (Chemtech, May 1996, p. 26-29) discovered that heating glutamic acid and aspartic acid gives a copolymer of the two amino acids. Further, other amino acids, which are unable to form polymers on their own, can be reacted with glutamic acid and/or aspartic acid to give copolymers. A feature of these xe2x80x9cthermal proteinsxe2x80x9d or xe2x80x9cprotenoidsxe2x80x9d is that they have nonrandom distribution in the amino acid sequence. This observation has led to the development of a unique research direction which is based on the origin of life based on proteins which can be obtained under terrestrial conditions. Thermal proteins have a molecular mass of up to 9000, which is low compared with natural proteins, and are therefore nontoxic and thus biocompatible with living systems. They are used, for example, in the microencapsulation of pharmaceuticals (U.S. Pat. Nos. 4,963,364, 4,925,673), as artificial skin (U.S. Pat. No. 4,996,292) or as active ingredient for improving memory performance (U.S. Pat. No. 5,373,085). The industrial use as inhibitors of mineral deposition in cooling-water systems is also described (U.S. Pat. No. 4,534,881). A further important advantage is their biodegradability.
The discussion of the prior art shows that silicone-protein copolymers are known, but that they hitherto have serious disadvantages. Either the copolymers are insoluble in water because the peptide component contains amino acid units carrying protective groups, or they are soluble in water, but then have a bond between peptide and silicone moiety which is sensitive to hydrolysis. The known processes for the preparation of such silicone-protein copolymers also have considerable disadvantages. They are either complex, multistage preparation processes in which toxic substances are often required, or are simple processes such as the silylation of peptides. The products cannot, however, be expected to have a true silicone effect.
An object of the invention, then, was to find new types of silicone-peptide copolymers which are soluble in water and at the same time are highly molecular and thus substantive. In addition, they should contain relatively long poly(dimethylsiloxy) units and thus exhibit a significant silicone effect. An other object was to find a process which is easy to carry out and does not require toxic reagents. These and other objective will become apparent to the practioner upon reading the specification.
Surprisingly, it has now been found that thermal copolymerization of natural and unprotected amino acids, in particular aspartic acid and glutamic acid with organo-functional polysiloxanes, give polypeptide-polysiloxane copolymers which could be converted into a water-soluble form and display a true silicone effect.
The chemical combination of such thermal proteins with silicones to give silicone-protein copolymers is not known. Surprisingly, it has been found that, despite the drastic reaction conditions, such as temperatures of above 170xc2x0 C. in a pH-acidic amino acid melt, reactive organopolysiloxane can be incorporated into the peptide with retention of the dimethylsilicone chains during the thermal polymerization of, in particular, aspartic acid and glutamic acid and other amino acids.
The invention thus provides new types of polypeptide-polysiloxane copolymers, processes for their preparation and their use as interface-active substances.
The present invention provides, in a first embodiment, polypeptide-polysiloxane copolymers consisting of at least one polysiloxane unit 
where the index m is a positive integer in the range m=1-52, of the general average formula I: 
where
R1=alkyl radical, preferably having from 1 to 4 carbon atoms,
R2=R1 and/or -sp-
where
-Sp -=divalent spacer between siloxane and another functional group, silicon atom and spacer being linked via a silicon-carbon bond, in particular a divalent alkylene radical having, preferably, from 1 to 20 carbon atoms, which is optionally branched, and may contain double bonds or aromatic rings, and heteroatoms, in particular oxygen, nitrogen or sulfur,
the indices a and b are integers in the ranges a=0-200 and b=0-50,
with the proviso that when a=b=0 and when b=0 and axe2x89xa00, at least one R2=-sp- in each case,
and of at least one polypeptide unit 
where
therm. protein is a structure of the general average formula II: 
or of the formula III: 
which is linked to the polysiloxane unit via a divalent functional group
-FG-
either via the C-terminal end, the N-terminal end or both ends of the polypeptide unit, and is a structural unit
xe2x80x94CH(OH)CH2xe2x80x94 or xe2x80x94CH(OH)CH2Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CH(CH2CO2H)COxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94CH(NH2)COxe2x80x94 or xe2x80x94CH(CO2H)NHxe2x80x94
and optionally additional links between polysiloxane and polypeptide units result via the radicals R4 and/or R5 
where
R3=R4 or R5,
where
R4=is identical to a radical of an amino acid and xe2x80x94(CH2)4xe2x80x94NHxe2x80x94R6,
where
R6=H (lysine) or 
R5=xe2x80x94CH2xe2x80x94CH2xe2x80x94COxe2x80x94R6 
where
R6=OH (glutamic acid) or 
xe2x80x83c, d, e and f are positive integers including 0,
with the proviso that
the indices c, d, e in formula II and c, d and f in formula III are not all 0,
in particular exe2x89xa00, when c=0,
c and dxe2x89xa00, when e or f=0, and
the molecular mass of the polypeptide unit is between about 250 and about 9000 and the weight ratio of polysiloxane units and polypeptide units in the polypeptide-polysiloxane copolymer is between about 1:99 and about 99:1.
Particularly preferred polypeptide-polysiloxane copolymers are those wherein:
R1 is CH3, m=2-32, a=8-10, b=0-30
Where, when b=0, both radicals R2 then correspond to -sp-;
m=2-7, a=8-40, b=0-15, where when b=0, both radicals R2 then correspond to -sp-;
c, d, and e in formula II or c, d and f in formula III do not equal 0 and the weight ratio of the polysiloxane units an the polypeptide units in the polypeptide-polysiloxane copolymer is between about 5:95 an about 55:45;
c in formula II or formula III=0 and d and e in formula II or d and f in formula IIIxe2x89xa00
and R3=R5 or xe2x80x94CH2xe2x80x94COxe2x80x94R6 
where
R6 is OH (aspartic acid) or 
xe2x80x83and the weight ratio of polysiloxane units and polypeptide units in the polypeptide-polysiloxane copolymer is between about 5:95 and about 55:45.
c and d in formula II or formula III=0, and e or f in formula II or formula IIIxe2x89xa00
and R3=xe2x80x94CH2xe2x80x94COxe2x80x94R6 
where
R6 is OH (aspartic acid) or 
xe2x80x83and the weight ratio of polysiloxane units and polypeptide units in the polypeptide-polysiloxane copolymer is between about 5:95 and about 55:45.
-sp- is selected from the group consisting of:
xe2x80x94(CH2)3xe2x80x94, xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CH2xe2x80x94 and xe2x80x94(CH2)3xe2x80x94NHxe2x80x94(CH2)2xe2x80x94 and
-FG- is selected from the group consisting of:
xe2x80x94CH(OH)CH2xe2x80x94 or xe2x80x94CH(OH)CH2Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CH(CH2CO2H)COxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94CH(NH2)COxe2x80x94 or xe2x80x94CH(CO2H)NHxe2x80x94.
Polypeptide-polysiloxane copolymers which are especially particularly preferred and are those wherein the amino acids is selected for example, from the group consisting of glycine alanine, valine, leucine, isoleucine, phenylalanine, proline, serine, threonine, tyrosine, asparagine, glutamine, arginine, tryptophan, histidine, cysteine, methionine, aspartic acid and glutamic acid.
Preferred examples of compounds according to the invention are:
A) 
xe2x80x83in which 
xe2x80x83(m=2) is identical to a polysiloxane unit of the following structure: 
where
R1=CH3 
both R2=-sp-
sp=xe2x80x94(CH2)3xe2x80x94,
a=8
b=0
and 
is identical to a polypeptide unit of the following structure: 
where
R3=xe2x80x94CH2CO2H or (CH2)2CO2H
c=0
d and fxe2x89xa00, and the ratio d:f is approximately 1:6,
FG=xe2x80x94NHxe2x80x94,
the molecular mass of the polypeptide unit is about 500 and the weight ratio of polysiloxane to polypeptide units in the copolymer is 1:9.
B) 
where the polysiloxane and the polypeptide units correspond to the structures given in Example A), where
R1=CH3 
R2R1 
-sp-=xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CH2xe2x80x94
a=20
b=5
and
where
R3=xe2x80x94CH2CO2H or xe2x80x94(CH2)2CO2H
c=0
d and fxe2x89xa00, and the ratio d:f is approximately 1:6,
FG=xe2x80x94CH(OH)CH2xe2x80x94,
the molecular mass of the polypeptide unit is about 2000 and the weight ratio of polysiloxane to polypeptide units in the copolymer is 3:7.
C) 
where polysiloxane and polypeptide units correspond to the structures given in Example A),
where
R1=CH3 
both R2=-sp-
-sp-=xe2x80x94(CH2)3xe2x80x94,
a=40
b=2
and
where
R3=xe2x80x94CH2CO2H or xe2x80x94(CH2)2CO2H
cxe2x89xa00 and R4=xe2x80x94CH2SH (cysteine)
d and fxe2x89xa00, and the ratio d:f is approximately 1:4,
FG=xe2x80x94NHxe2x80x94,
the weight ratio of cysteine on the polypeptide moiety is about 5%,
the molecular mass of the polypeptide unit is about 1500 and the weight ratio of polysiloxane to polypeptide units in the copolymer is 4:6.
D) 
where the polysiloxane unit corresponds to the structure given in Example A), where
R1=CH3 
both R2=-sp-
-sp-=xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2xe2x80x94NHxe2x80x94(CH2)4xe2x80x94
a=18
b=0
and the polypeptide unit corresponds to the following structure: 
where
R3=xe2x80x94CH2CO2H
c and d=0
exe2x89xa00
FG=xe2x80x94CH(NH2)COxe2x80x94 or xe2x80x94CH(CO2H)NH xe2x80x94,
the molecular mass of the polypeptide unit is about 1000 and the weight ratio of polysiloxane to polypeptide units in the copolymer is 1:9.
A feature of this new class of compound according to the invention is that they can be obtained in a simple process and without using protective groups or solvents. A particular advantage is that the starting materials are defined compounds, namely (natural) amino acids and organically modified polysiloxanes. This is in contrast to those processes which start from protein hydrolysates, which can differ greatly from one another depending on the source of the protein (animal or vegetable), preparation process (pH, reaction temperature, reaction time) and the storage time of the solution. Reproducibility of the product quality can thus be ensured only with difficulties.
Another important advantage of the present class of compound is that their surface-active properties can be adjusted in a targeted, tailored and reproducible manner. This is achieved in a simple manner through the choice of the starting compounds and their weight ratio. Through the choice of the weight ratio of amino acids to polysiloxane, usually between about 95:5 and about 40:60, the proportion of polydimethylsiloxane units is essentially predetermined, which will affect the surface-active properties. Another parameter is the structure of the polysiloxane. It is obvious that the arrangement and the number of functional groups in the polysiloxane has a big effect on the properties of the copolymer. The siloxane can carry functional groups on both ends of the chain or in side positions in varying number. It makes a difference to the product properties what chain length, for example, a terminal-functionalized polysiloxane has or what chain length and how many functional groups per chain a comb-like polysiloxane have. Another way of modifying the surface-active properties is the nature and ratio of amino acids used to one another. Thus, for example, the addition of hydrophobic amino acids such as phenylalanine can reduce the hydrophilicty of the polypeptide moiety. In addition, the molecular weight of the copolymer can be adjusted by the way in which the reaction is carried out, in particular by the temperature and the duration of heating.
An additional important feature, is that, in contrast to the protein-polysiloxane copolymers known from the literature, the inventive compounds comprise poly(dimethylsiloxy) chains which, as a hydrophobic moiety together with the hydrophilic polypeptide moiety, form a surfactant as a result of a real chemical bond, and, therefore, a true silicone effect is achieved. Another advantage is that the copolymers, depending on the type of work-up, can be obtained in a water-insoluble or a water-soluble form. In the water-insoluble form they can, for example, be incorporated into nonpolar media. They can, however, also be obtained in a water-soluble form as aqueous solutions or, after removal of the water, in solid form. They form a dry, readily flowable powder, which mixes with water in any ratio to form clear solutions. It can be recovered again from the solutions by distilling off the water. It thus differs considerably from protein hydrolyzate organosilane or organosiloxane solutions as described in EP-A-0 540 357, which, after removal of the water, form a hard film which no longer dissolves in water.
The present invention further provides for a process for the preparation of the above-described polypeptide-polysiloxane copolymers by thermal polymerization of amino acids of the general formula: 
where R7 is identical or different and is the residue of an amino acid such as in glycine, alanine, valine, leucine, isoleucine, phenylalanine, proline, serine, threonine, tyrosine, asparagine, glutamine, arginine, lysine, tryptophan, histidine, cysteine, methionine, aspartic acid, glutamic acid, in the presence of organopolysiloxanes having reactive groupsxe2x80x94RG in the formula (I) defined above.
The organopolysiloxanes to be used are known from the prior art and are available commercially or can be prepared readily in a known manner. Terminally epoxy- or amino-functionalized polysiloxanes are obtained, for example, by hydrosilylation of allyl glycidyl ethers or allylamine to a terminally functionalized hydridosiloxane. Comb-like aminopropylsiloxanes are prepared, for example, by condensation and alkaline equilibration of aminopropyldialkoxysilanes and cyclic siloxanes.
Examples of suitable organofunctional polysiloxanes are: 
The preparation process is described below by way of example. In a first stage, glutamic acid, for example, is melted at about 170-180xc2x0 C., under which the cyclic amide, pyroglutamic acid (2-pyrrolidone-5-carboxylic acid) is formed by elimination of water. Instead of glutamic acid, it is also possible to use proline or a polar, high-boiling solvent such as N-methylpyrrolidone or sulfolane. Aspartic acid is then added, and the melt or the high-boiling solution is heated at 160-220xc2x0 C. In this process polysuccinimide forms, which, in cases where glutamic acid is used, also contains glutamic acid units. The duration and temperature of heating is used to control the molecular mass of the growing polymer. The longer the heating time and the higher the temperature, the higher the molecular mass. In the next step, the organofunctional polysiloxane is added dropwise. The heating time after all of the polysiloxane has been added in turn influences the molecular mass of the copolymer formed. The melt is poured out and, after cooling, forms a glasslike mass, which can be readily pulverized by grinding. This is the water-insoluble form of the polypeptide-polysiloxane copolymer.
The water-soluble form of the polypeptide-polysiloxane copolymer is obtained by treating the copolymer with alkaline aqueous solution, for example with aqueous sodium hydroxide solution. If, during this procedure, the neutral point is exceeded, then aqueous hydrochloric acid can, for example, be used for neutralization. The resulting aqueous solution of the copolymer can be used either directly or the water can be distilled off to obtain a water-soluble powder.
In one process variant, the pyroglutamic acid melt is first cooled to about 120xc2x0 C., and then the organofunctional polysiloxane is added. After some time the temperature is increased to 170xc2x0 C. and only then is the aspartic acid added. This process variant has proven advantageous particularly for comb-like polysiloxanes.
The present invention also provides for the use of the polypeptide-polysiloxane copolymers in surface-active applications, in particular as silicone surfactants.
The polypeptide-polysiloxane copolymers according to the invention can be used in various applications. They are particularly suitable for use in aqueous media, where they exhibit their performance due to their interfacial activity and their affinity to surfaces. Depending on their structure, they can improve surface structure when used in plastics. They can also be used as oil-in-water or water-in-oil emulsifiers or as stabilizers in emulsions, or, for example, in cosmetic preparations for the cleansing of skin and hair, for improving foaming and for the conditioning of hair and/or for achieving a pleasant feel on the skin. As protein derivatives, they can be used as skin moisturizers or as agents for alleviating irritation of the skin. The polypeptide-polysiloxane copolymers according to the invention are of course frequently used together with surfactants and other additives for influencing surface quality. All said formulations can comprise known additives, such as, for example, wetting agents, surfactants or emulsifiers from the classes of anionic, cationic, zwitterionic, amphoteric or nonionic surface-active substances, for example fatty alcohol sulfates, fatty alcohol ether sulfates, alkylsulfonates, alkylbenzenesulfonates, sulfosuccinic alkyl esters, quaternary ammonium salts, alkyl betaines, carboxamidoalkyl betaines, derivatives of monomeric saccharides and saccharides with high degrees of condensation, ethoxylated fatty alcohols, fatty acid alkanolamides or ethoxylated fatty acid esters, thickeners, such as, for example, kaolin, bentonite, fatty acids, higher fatty alcohols, starch, polyacrylic acid or derivatives thereof, cellulose derivatives, alginates, petroleum jelly or paraffin oil.
In addition, use of the compounds according to the invention as textile auxiliaries or as additives in paints and surface coatings is also possible.